Conventionally, a purge system of a vehicle for purging fuel vapor is known to have a valve device (e.g., a tank-sealing valve). The tank-sealing valve opens an air space provided in the fuel tank to the outside via a canister so that fuel is supplied smoothly into the fuel tank in a refueling. Further, the tank-sealing valve restricts an increase of a pressure (e.g., an inside-tank pressure) in the air space. That is, the tank-sealing valve has a first valve member opening or closing the fuel tank to the outside. By operating the first valve member, fuel including fuel vapor escapes and flows out of the fuel tank. The tank-sealing valve is required to be downsized, to be easy to handle pipes, and to be located as close to the fuel tank as possible. Based on such requirements, the tank-sealing valve has a passage configuration, for example, including a first passage, a second passage, and a specific chamber.
Fluid (i.e., escape fluid) flowing out of the fuel tank flows through the first passage when the first valve member is open. The second passage is provided separately from the first passage, and the escape fluid flows through the second passage when a second valve member disposed separately from the first valve member is open. The specific chamber is provided at an outer periphery side of a pipe providing the first passage and at an outer periphery side of the first valve member. The escape fluid flows through the specific chamber just before flowing into the second passage when the second valve body is open. In the specific chamber, the escape fluid flowing into the specific chamber collides an outer surface of the pipe or the like and is divided into two divided flows. The two divided flows are joined again at downstream of the pipe, or the like, in a flow direction of the escape fluid and then flow into the second passage.
The tank-sealing valve further has, for example, an electromagnetic solenoid, which generates magnetic attractive force when a power source mounted in the vehicle applies electric force to the tank-sealing valve. The first valve member is operated to be open based on the magnetic attractive force generated by the electromagnetic solenoid. When the first valve member is open, the escape fluid flows into the first passage via the first valve member and flows out of the fuel tank (see JP-A-2006-226457 corresponding to U.S. 2006/0185735 A1).
The second valve member has a structure as a check valve. The second valve member is open so that the escape fluid flows into the second passage via the second valve member when a pressure of the escape fluid is higher than a predetermined valve-opening pressure. The second valve member is closed so that the escape fluid is restricted from flowing into the second passage when a pressure of the escape fluid is lower than a predetermined valve-closing pressure. Accordingly, the tank-sealing valve is capable of restricting an increase of a pressure in the fuel tank by opening or closing the second valve member without an electric supply from the power source. The second valve member and peripheral parts configure a relief valve, separately from a main part of the tank-sealing valve including the first valve member, the first passage, the specific chamber, or the like. The second valve member and the peripheral parts are simply referred to as the relief valve.
In the tank-sealing valve, a large pressure loss of the escape fluid is caused in the specific chamber when the relief valve is open, and frequency of opening or closing of the relief valve becomes high. As a result, the relief valve may be damaged earlier. Specifically, a large pressure loss is caused in the specific chamber since the escape fluid collides the outer surface of the pipe or the like and is divided into the two divided flows, and the two divided flows are joined again.
Furthermore, the tank-sealing valve is required to have the passage configuration including the first passage, the second passage, and the specific chamber based on the requirements described above. Therefore, the specific chamber is difficult to be omitted.